The present invention relates to a lead storage battery and particularly to improvements in a closed type lead storage battery having a plastic container, wherein the construction of the bond between the terminal poles and a cover for the plastic container is improved to provide a leakproof lead storage battery.
In lead storage batteries using dilute sulfuric acid as the electrolyte, leakage of the electrolyte is the most detestable problem as it damages not only the battery itself but also the equipment which uses the battery.
Such a leakage phenomenon takes place mainly (1) between the plastic container and the cover, (2) around the terminal poles of the battery, and (3) between the cells in the case of the monoblock battery. Thus, prevention of this leakage phenomenon has been a long-standing problem in lead storage batteries, but no preventive method has been found which is simple and yet reliable.
A conventional method of bonding the terminal poles to the cover will now be described with reference to the drawings.
As shown in FIG. 1, there is a step of filling a bonding agent 8 into a recess in the back of a cover 5 in which a U-shaped connector 11 connecting cells is embedded, and into an annular recess in an outer peripheral portion bonded to a plastic container 1, and there is a subsequent step of invertedly fitting the plastic container 1 having inserted therein a group of plates 2 over the cover 5 lying with its back side directed upward, and then bonding them together. At this time, a terminal pole 3 is not embedded in the bonding agent 8 but projects outwardly through a pole hole 12 in the cover 5. After going through the step of curing said bonding agent, the battery is brought back to its normal position, as shown in FIG. 2. Then, a rubber packing 13 is fitted on the terminal pole 3 so that a bonding agent 14 for fixing the terminal pole 3 to the cover 5 cannot fall down through the pole hole 12 onto the group of plates 2 on the cell chamber side. The front end of the terminal pole is then soldered to a Faston tab terminal 7. After the step of filling the bonding agent 14 into the recess has been performed, the bonding agent 14 is cured to thereby bond the terminal pole and the cover together.
However, this method of producing batteries requires that the operation of bonding the terminal poles to the cover to be performed in two stages, i.e., on the U-shaped connector portion connecting the cells and on the terminal pole portion; thus, not only is the number of steps excessive but also it takes a long time for the bonding agent to cure. Therefore, there has been a disadvantage that too much time is taken for completion of the battery.